The present invention relates generally to rolling mill apparatus for handling elongated, hot rolled articles such as hot rolled bars. More particularly, the invention relates to apparatus, in a hot rolling mill, which switches hot rolled bars alternately back and forth between two diverging paths.
Conventional switches, previously employed in hot rolling mills, included both vertical switches, which diverted alternate bars to paths diverging above and below the switch, and horizontal switches which diverted bars alternately to paths diverging to the left and to the right of the switch. Most such switches comprised a member, elongated in the direction of movement of the bar, pivoted at one end and having edges or surfaces which engaged a bar to divert or guide the bar along one path or another. A so-called "knife switch" fits this description.
Among the drawbacks of conventional, previously employed switches were that such switches couldn't be changed to divert a second or approaching bar, which had not yet arrived at the switch, until the tail of a preceding bar already undergoing switching was completely past the switch; and it was necessary to accelerate the tail of the preceding bar so as to provide a gap between it and the head of the approaching bar. Also, there was the danger of a head-on collision between the nose of the switch and the head of the approaching bar if the switch had not completed its movement to divert the approaching bar before the head of the approaching bar reached the switch. Such a collision could cause damage to the bar or cobbling (i.e., tangling), requiring a shut down of that portion of the mill where the cobble occurred, for removal of the cobble which was then scrapped.
Because of the relatively short time available to change the switch for diverting bars from one path to another, it was often necessary to use a fast-acting switch which, because of the rapidity of its movement, produced a slamming action or a relatively large impact against the approaching bar. Because the bar was relatively hot as it passed through the switch (e.g., 1700.degree.-1900.degree. F) there was a danger that the slamming action of the switch could deform the bar to an extent greater than that from which the bar could recover; and an unrecoverable bend in the bar could cause cobbling, among other things.
If the switch was moved to divert the approaching bar before it reached the switch, there was a danger of exerting pressure on the tail end of the preceding bar, causing a kink which had to be cut off or straightened.